Computer systems and technology employing electromagnetic frequencies, such as radio frequencies, to track the location of an object in an environment are generally known in the art. Many systems track items through area detection tracking. Area detection tracking commonly uses a single computer linked to radio frequency receivers placed periodically throughout a facility. The receivers attempt to locate tag transmitters placed on objects in the facility. The receivers employ a single antenna with a predetermined bandwidth. The larger the bandwidth the larger the potential tracking area to be covered but also the greater amount of energy required to operate the system. When the tag transmitter enters the bandwidth of a receiver, the receiver receives an identification code transmitted by the tag and relays the code to the computer. The computer then records the location of the object bearing the tag transmitter based on the location of the receiver in the facility that relayed the identification code.
Area detection tracking possesses many shortcomings. First, the systems typically provide insufficient coverage to track items to an acceptable resolution. Typically, area detection systems place receivers at stations or sites where objects are expected to be, such as the next station in a manufacturing process. The area detection system in those cases is merely a location verification system. The system reports that an item has arrived at its designated station, has arrived late, or at the incorrect station. However, the system has no ability to locate an item in a facility that has deviated from its designed course. Additionally, location verification systems are easy to intentionally avoid. Because receivers are only placed in particular locations with only a predetermined transmission receiving field, a deviant individual with knowledge of the system or receiver technology could remove items from the facility without detection.
Area detection tracking systems also do not provide any information on the direction in which an item bearing a transmitter has moved once it leaves the area-detection field of a receiver. These systems use point-to-point-tracking schemes. These schemes track the history of the movement of an object as it passes within the radio frequency fields of each receiver but cannot determine the direction of movement of an item. In such cases, the area detection systems provide information on the last recorded location of an object but provide no information on the object's current location until the object passes within the radio frequency field of another receiver. In large facilities, such as manufacturing plants, office buildings, warehouses and hospitals, many paths of movement could branch from each area detection point making it difficult, if not impossible, to know the current location of an item when the item is not within the radio frequency area of a receiver.
In an attempt to overcome the shortcomings attributable to area detection systems, arrays of receivers are distributed in a grid pattern with the size of an detection area determined by the predetermined spacing of receivers based on the width of its radio frequency field. In a grid area detection scheme, radio frequency coverage of facility is increased closing the space between receivers thereby providing increased data collection and higher resolution for point-to-point tracking—the more receivers, the closer together, the greater the ability to plot the movement of the object throughout the facility.
Grid area detection systems carry serious disadvantages. First, grid systems are typically only used in smaller facilities with open floor plans such in manufacturing facilities for semiconductors, high-priced electronics or medical equipment. The grid area detection systems require many receivers in close proximity that make the capital and installation of such a system cost prohibitive in large facilities or in facilities with many corridors, rooms, multiple floors, and numerous points of ingress and egress. Second, grid detection systems are expensive to operate in terms of energy costs to run the numerous receivers. To minimize the operational costs of continuously running all receivers and transmitters, motion detection devices and circuits are employed in the facility to activate receivers only when objects are in motion in close proximity. However, the addition of motion detection technology to the system complicates operation of the detection efforts and adds additional installation and capital costs as well as complexities to the programming required to operate the system.
To overcome the disadvantages of the area detection methods, more complex tracking systems such as time-of-arrival and signal-strength methods have been developed to pinpoint and continuously track the location of an object within a facility. In such programs, receivers are placed strategically throughout a facility. As an object moves through a facility, the exact location of an object is determined by a time-of-arrival determination based on the amount of time it takes multiple receivers to receive a transmission from an item tagged with a transmitter. Based on the timing receipt of the signal from the multiple receivers, the computer can determine the location of items by correlating the time differential of signal receipt as a distance of the object from each receiver. Likewise, a signal-strength method determines the location of an object from the strength of its transmission received by multiple receivers. Here, signal-strength directly correlates with the distance of the object from the receiver, with the transmission signal being stronger the closer it is to a receiver.
The time-of-arrival and signal-strength methods also have disadvantages. Although these systems can determine the exact location of an object, they can only do so if the transmission from an object falls within the radio frequency area of at least three receivers. Accordingly, many receivers must be placed throughout a facility to provide sufficient coverage. Additionally, the tag transmitter assigned to an object often must transmit through walls, machinery and other obstructions that may absorb the transmission from the transmitter of the object introducing unpredictable levels of attenuation of signal strength or time delay in the receivers' receipt of the signal. Obstructions may also deflect or reflect the signal of the transmitter projecting a false or ghost signal that does not correspond with the true location of the object. The time-of-arrival and signal-strength methods of tracking also involve complex transmitter and receiver circuitry and computer algorithms to determine the location of an item from the signal receipt by multiple receivers adding to the cost of the system and operational complexities. Because of these constraints, such systems typically are employed in small manufacturing facilities and offices where valuable items are often transported throughout the facility requiring continuous and detailed information on the items whereabouts.
Prior art radio frequency locating systems use single-frequency technology in locating systems. A limited number of other radio frequency locating systems use spread-spectrum radio communications in the high megahertz frequency ranges. Operation in the high frequency ranges is required to provide a larger bandwidth to increase the area of detection and the strength of the detection field over the area. Because of operation at these high frequencies, Federal Communications Commission licensing may be required to operate the system. Other systems may be operated in ranges not requiring licensing but may interfere with other systems in the facility such as telecommunication systems, computers, and equipment sensitive to the radio frequencies. Additionally, other systems in the facility may also emit radio frequencies in close proximity to the signal of the transmitter introducing noise that will project false locations or interfere with the calculations performed by the system to determine the location of an item.
Some low frequency detection systems are also known in the art. In these systems, transmitters operating in low frequency ranges transmit identification information from low range transmitters to receivers to log the location of a person or object. These systems because of the inaccuracy and stability of low-frequency transmissions require close proximity transmissions between the transmitter and the receiver. This transmission range is nominally two feet or less. Such systems may require passing or waving the transmitter next to or near the receiver or even a more active component of swiping the transmitter through a component linked to the receiver such as magnetic card reader or a scanning device. The close proximity required to record a transmission from the identification transmitter makes such systems unreliable to passively locate and monitor items in a facility.
Moreover, prior art radio frequency location systems are often ineffective in tracking the location of individuals in a facility. Individuals in a facility often find the continuous tracking of their location as invasive and will attempt to evade continuous monitoring of their location by avoiding receivers when and where possible. Intentional avoidance of receivers by individuals makes tracking the individuals as well as other objects that they may be transporting difficult and at times inaccurate.
Finally, prior art radio frequency location systems provide the limited role of documenting movement of an item or verifying its location in a facility. In some cases, the continuous monitoring of an item may be reviewed and evaluated to track down the last known location of an object or to determine that an item has deviated from its expected course in the facility. In such cases, reactive measures can be taken by personnel in the facility to either locate the object or attempt to learn why the item deviated from its expected path. However, prior art systems do not provide real-time responses to the movement of items in a facility to attempt to stop or curb the unauthorized movement of an item by communicating warnings to alert the mover of the item of the unauthorized activity, alerting security, and enabling users of the system to proactively locate an item in the facility. Prior art systems do not provide immediate response and action to the unauthorized movement or activity associated with an item. In the same course, known area detection systems are not coupled with third party communication and response devices in a facility to permit the system to utilize systems already present in the facility to aid in the location of an item or to immediately respond to unauthorized activities.